Angled gas ports?

[FUNCTIONAL]

So actual port size not important for this discussion.

I've heard some doing angled gas ports at 45deg. Mild rumors that you get a bit more dwell time and can potentially run a smaller port everything else being equal.

That's about all I've seen. Any one in here have information on it? Benefits, disadvantages, etc.

 

[TheOE800]

The Ruskis used to on the AK platform, but stopped because of bullet jacket deformation at the edge of the elliptical port where it caught a land in the rifling. LMT presently does it and I’ve heard anecdotal tales of small boutique/individuals who still do angled gas ports. Contrary to popular belief, LMT does not ensure their elliptical gas port is centered in the groove based on multiple barrels I’ve scoped so they’re not concerned about the jacket deformation issue like the Ruskis were or feel it isn’t important.

 

[hlee]

If Russian 7.62x39 ammunition is not substantially more consistent than what we get over here, it is hard to imagine they could separate the effects of an angled gas port from the crap ammo.

That said, if the increased cost of manufacturing could be passed to the customer, and justified with a measurable and marketable increase in end user satisfaction, then you would see more angled gas ports in the market.

 

[TheOE800]

If Russian 7.62x39 ammunition is not substantially more consistent than what we get over here, it is hard to imagine they could separate the effects of an angled gas port from the crap ammo.

It’s rather well documented in the AK literature actually.

 

[TonyTheTiger]

I've got two angled port barrels. They work. I think the idea behind the ones I have is to be able to use unusually long gas systems on a given barrel length.
I've recovered quite a few bullets out of the berm, never seen anything weird on them.

 

[FUNCTIONAL]

Anyone ever see anything on port erosion compared to 90deg port?

As far as port placement the bit I've read is inconclusive between random placement vs in the groove.

 

[TonyTheTiger]

Anyone ever see anything on port erosion compared to 90deg port?

Send me a bore scope and I'll tell you. I've got a pulled barrel with 12-13k on it and a new one with maybe 800 on it.
One of the barrels is a 14.8" rifle gas system, I think the additional dwell time with the angled port must be doing something, because it works great even though it shouldn't.

 

[FUNCTIONAL]

Send me a bore scope and I'll tell you. I've got a pulled barrel with 12-13k on it and a new one with maybe 800 on it.
One of the barrels is a 14.8" rifle gas system, I think the additional dwell time with the angled port must be doing something, because it works great even though it shouldn't.

Why do you say it shouldn't?

 

[iktomi]

I have a few barrels made by MicroMOA from the later 20-teens (2016?). IIRC, all of them have angled gas ports (angled such that they penetrate the bore farther to the muzzle).

All of the builds have atypical BCG/buffer masses and springs.

I think they were on very good blanks from Feddersen (a very good manufacturer).

They all performed very well.

My conclusion (sample size 3) is that the angled ports did not have a detrimental effect on accuracy (.50-.75 MOA).

The 16 inch rifle gas (+45 degree) system is my favorite atypical build to date. Low mass system, it cycled well suppressed when tuned for suppressed, and cycled 100% (250ish 55gr run-and-gun rounds) when I added gas for unsuppressed.

 

[TonyTheTiger]

Why do you say it shouldn't?

Because a 14.8" RLGS barrel has almost no dwell time. With the port angled towards the chamber it gains a tiny bit of dwell and I suspect it needs all it can get.

 

[FUNCTIONAL]

Because a 14.8" RLGS barrel has almost no dwell time. With the port angled towards the chamber it gains a tiny bit of dwell and I suspect it needs all it can get.

Fair enough, wasn't quite sure where you were going with that. Everything I've read had it angled towards the muzzle but I guess it works both ways in your case.

 

[TonyTheTiger]

Fair enough, wasn't quite sure where you were going with that. Everything I've read had it angled towards the muzzle but I guess it works both ways in your case.

I have seen them angled forward, but that is directly at odds with your statement in the OP: "I've heard some doing angled gas ports at 45deg. Mild rumors that you get a bit more dwell time and can potentially run a smaller port everything else being equal."
Angled forward would equal less dwell time and a bigger port needed.

 

[bill alexander]

Angled gas ports are a method of controlling the erosion such that the area remains constant for higher round counts and the pressure drop across the port is more consistent. The Russians abandoned the complexity of indexing angled ports through the barrel groove during testing of the AK74 as the gun is tolerant of port erosion within its life cycle.

It is extremely difficult to correctly form the internal edges of an angles port without use of EDM to chamfer any sharp edges. Thus accuracy will suffer.

The dwell time created by the angle does exist but is only nominal even for a 45 degree port.